The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Supporting washers made of metal or synthetic material have been known for a long time, having at their center a hole intended to allow the stem of a connecting element comprising a head to pass through, for example a screw or a rivet, while still retaining the head of said connecting element, the dimension of the hole being greater than or equal to that of the stem and less than that of the head. These known washers can comprise a bowl around the central hole for the purpose of housing the head of the connecting element.
These washers increase the surface on which the screw bears, preventing, in this way, the screw head from damaging the material placed under it in the case where a supporting washer is not used, by distributing the force exerted by the screw over a larger surface.
Disadvantages occur only rarely in the case where the material placed under the washer is a metal, but occur more often in the case where this material is wood, a synthetic material, or an elastomer. Indeed, the circumferential edge of known supporting washers is a surface perpendicular to the general plane of known washers, the lower edge of the circumferential edge of known washers, formed by the meeting between said surface perpendicular to the general plane of said known washers and the lower surface plane of said known washers, exerts a shearing action in the material on which the known washers bear. This shearing is barely discernible of even non-existent, in the case where this material is a hard material, for example a metal material, but it occurs as soon as the screw is tightened in the case where this material is a synthetic material, and even more in the case where this material is an elastomer. As mentioned hereinabove, this shearing can occur as soon as the screw is tightened or as soon as the rivet is applied, but even more when the assembly assembled by means of the connecting element, using said known supporting washers, is subjected to forces being exerted in varied directions. An example of this is given in the field of elastomer junctions such as used to connect the ends of a conveyor belt. These reinforced elastomer junctions are fixed at the ends of the conveyor belt using screws or rivets that successively pass through the upper plate of these junctions, the ends of the conveyor belt and the lower plate of these junctions.
French Patent No. 2 803 836 shows this application. Note that in the case of this patent, inserts embedded in the elastomer material of the plates of the junction are used to receive the screw heads. But, during manufacture, the setting up, in particular that of the upper insert forming a bowl for the purpose of receiving the screw head, is expensive, and attempts have been made to use a supporting washer as a replacement for the upper insert. But disadvantages, already described, were encountered with the known supporting washers. This led to the utility of creating new supporting washers, able to eliminate these disadvantages.
In the same application for reinforced elastomer junctions intended to connect the ends of a conveyor belt, this shearing is even more accentuated due to the use, in the case of certain conveyor belts, of scrapers formed of blades applied against the surface of the conveyor belt in motion, these blades being intended to remove the debris of the transported material remaining on said surface of the conveyor belt, for example coal or ore. These blades encounter the supporting washers and accentuate the shearing effect described hereinabove, all the more so that these blades are often provided with tungsten steel edges, which are particularly aggressive.